JAXB解组XML类强制转换异常

问题描述

我正在使用此来解组我的字符串xml并返回List类型。
这是我使用的方法。

I'm using this JAXB Collection Generics to unmarshall my string xml and return the List type.Here's the methods I used.

public static <T> List<T> unmarshalCollection(Class<T> cl, String s)
        throws JAXBException {
    return unmarshalCollection(cl, new StringReader(s));
}

public static <T> List<T> unmarshalCollection(Class<T> cl, Reader r)
        throws JAXBException {
    return unmarshalCollection(cl, new StreamSource(r));
}


private static <T> List<T> unmarshalCollection(Class<T> cl, Source s)
        throws JAXBException {
    JAXBContext ctx = JAXBContext.newInstance(JAXBCollection.class, cl);
    Unmarshaller u = ctx.createUnmarshaller();
    JAXBCollection<T> collection = u.unmarshal(s, JAXBCollection.class).getValue();
    return collection.getItems();
}

示例getter和setter：

Example getters and setters:

   @XmlRootElement(name = "person")
class Person{

    private String firstName;
    private String lastName;
    private String address;


    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "Person [firstName ="+firstName+" , lastName = "+lastName+" , address = "+address+"]";
    }

}

主要类别：

public static void main(String[] args) throws JAXBException {
        String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><person><firstName>Foo</firstName><lastName>Bar</lastName><address>U.S</address></person>";
        List<Person> p = unmarshalCollection(Person.class,xml);
        for(Person person : p ){
            System.out.println(person);
        }
    }

抛出异常

Exception in thread "main" java.lang.ClassCastException: org.apache.xerces.dom.ElementNSImpl cannot be cast to  com.Person
at com.JAXBUtil.main(JAXBUtil.java:62)

我做错了什么？任何想法？谢谢。

What did I do wrong? Any ideas?Thanks.

推荐答案

您的列表不是您期望的Person对象列表。由于java的泛型类型擦除，在尝试在循环中转换为person之前，您没有看到错误。

Your list is not a list of Person objects as you expect. Due to java's generic type erasure, you're not seeing the error until you try to cast to person in the loop.

尝试：

List<Person> p = unmarshalCollection(Person.class,xml);
for(Object person : p ){
   System.out.println(person.getClass());
}

参见

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